1. Field of the Invention
The invention relates to an arrangement with three superconductive phase conductors, which are arranged in at least one cryostat which conducts a cooling agent and which is composed of a pipe having a thermal insulation, and which is constructed of: a superconductive conductor as well as a dielectric and an electrically conductive screen surrounding the dielectric (U.S. Pat. No. 7,238,887 B2).
2. Description of Related Art
A superconductive cable or a corresponding phase conductor has an electric conductor of a material which changes over into the superconductive state at sufficiently low temperatures. The electrical direct current resistance of a correspondingly constructed conductor is zero with sufficient cooling as long as a certain current—the critical current—is not exceeded. Superconductive cables having cold and hot dielectric are known.
In a superconductive cable with cold dielectric, the superconductive conductor is surrounded by a dielectric composed of layers of insulation material. For example, bands composed of polypropylene which are laminated with paper can be used for the dielectric. Such a cable is composed, for example, of the superconductive conductor and a superconductive screen arranged concentrically relative to the conductor, wherein the conductor and the screen are separated from each other and spaced from each other by the dielectric. An appropriate cable is surrounded during operation by a cryostat which conducts a cooling agent, for example liquid nitrogen, and which is composed of two concentric metal pipes which are insulated from each other by a thermal insulation. The cooling agent penetrates the dielectric of the cable and, as a result, simultaneously is the impregnating agent for the cable.
In a superconductive cable with hot dielectric only the superconductive conductor is mounted directly in a cryostat through which a cooling agent flows. The dielectric and the screen composed in this case of an electrically normally conducting material, for example copper, are arranged outside of the cryostat.
U.S. Pat. No. 7,238,887 B2 discloses an arrangement with three superconductive phase conductors which are arranged together in a cryostat composed of two concentric pipes which are thermally insulated relative to each other. Each phase conductor is composed of a superconductive conductor, a dielectric surrounding the superconductive conductor, a superconductive screen or return conductor mounted above the dielectric. During operation of the arrangement, the three phase conductors are arranged in a cooling agent flowing through the cryostat. Accordingly, the construction of the arrangement corresponds to that of the described cable with cold dielectric.